[9fans] acme automatic dump

[roger peppe <rogpeppe@gmail.com>]

My laptop has been a bit flaky recently
which has brought this issue to the fore for me
(nothing like a few hours' lost work to prompt
some action!)

If my computer crashes, it would be great
if I didn't lose all my unsaved work in acme.

I'm thinking of adding some way to automatically
executing a Dump on a periodic basis.

I can think of at least two approaches:

1) implement the functionality inside acme itself
(e.g. with a command-line flag)

2) implement a way of triggering a dump through
the fs interface (e.g. by adding a root-level ctl
file and allowing a "dump" message).

The second is probably less work, but is harder
to get just right (you'd probably want a way to
check if anything has changed too, to avoid
needless churn when acme's sitting idle).

Has anyone already done something like this?
Any strong thoughts on which of the above
approaches is preferable, if any?